/* * fmd.c, parser frontend and utility functions for flashmap descriptor language * * Copyright (C) 2015 Google, Inc. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; version 2 of the License. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. */ #include "fmd.h" #include "common.h" #include "fmd_parser.h" #include "fmd_scanner.h" #include "option.h" #include <assert.h> #include <search.h> #include <string.h> /* * Validate the given flashmap descriptor node's properties. In particular: * - Ensure its name is globally unique. * - Ensure its offset, if known, isn't located before the end of the previous * section, if this can be determined. * - Ensure its offset, if known, isn't located after the beginning of the next * section or off the end of its parent section, if this can be determined. * - Ensure its size is nonzero. * - Ensure that the combination of its size and offset, if they are both * known, doesn't place its end after the beginning of the next section or * off the end of its parent section, if this can be determined. * In the case of a validation error, the particular problem is reported to * standard error and this function returns false. It should be noted that this * function makes no claim that the members of the node's child list are valid: * under no circumstances is any recursive validation performed. * * @param node The flashmap descriptor node to be validated * @param start Optional minimum permissible base of the section to be * validated, to be provided if known * @param end Optional maximum permissible offset to the end of the section to * be validated, to be provided if known * @return Whether the node is valid */ static bool validate_descriptor_node(const struct flashmap_descriptor *node, struct unsigned_option start, struct unsigned_option end) { assert(node); #if __GLIBC__ /* GLIBC is different than the BSD libc implementations: * The hdestroy() [function does] not free the buffers pointed * to by the key and data elements of the hash table entries. * vs: * The hdestroy() function calls free(3) for each comparison key in * the search table but not the data item associated with the key. */ ENTRY search_key = {node->name, NULL}; #else ENTRY search_key = {strdup(node->name), NULL}; #endif if (hsearch(search_key, FIND)) { ERROR("Multiple sections with name '%s'\n", node->name); return false; } if (!hsearch(search_key, ENTER)) assert(false); if (node->offset_known) { if (start.val_known && node->offset < start.val) { ERROR("Section '%s' starts too low\n", node->name); return false; } else if (end.val_known && node->offset > end.val) { ERROR("Section '%s' starts too high\n", node->name); return false; } } if (node->size_known) { if (node->size == 0) { ERROR("Section '%s' given no space\n", node->name); return false; } else if (node->offset_known) { unsigned node_end = node->offset + node->size; if (end.val_known && node_end > end.val) { ERROR("Section '%s' too big\n", node->name); return false; } } } return true; } /* * Performs reverse lateral processing of sibling nodes, as described by the * documentation of its caller, validate_and_complete_info(). If it encounters * a node that is invalid in a way that couldn't have been discovered earlier, * it explains the problem to standard output and returns false. * * @param first_incomplete_it First node whose offset or size couldn't be * determined during forward processing * @param cur_incomplete_it Last node whose offset or size is unknown * @param end_watermark Offset to the end of the unresolved region * @return Whether all completed nodes were still valid */ static bool complete_missing_info_backward( flashmap_descriptor_iterator_t first_incomplete_it, flashmap_descriptor_iterator_t cur_incomplete_it, unsigned end_watermark) { assert(first_incomplete_it); assert(cur_incomplete_it); assert(cur_incomplete_it >= first_incomplete_it); do { struct flashmap_descriptor *cur = *cur_incomplete_it; assert(cur->offset_known || cur->size_known); if (!cur->offset_known) { if (cur->size > end_watermark) { ERROR("Section '%s' too big\n", cur->name); return false; } cur->offset_known = true; cur->offset = end_watermark -= cur->size; } else if (!cur->size_known) { if (cur->offset > end_watermark) { ERROR("Section '%s' starts too high\n", cur->name); return false; } cur->size_known = true; cur->size = end_watermark - cur->offset; end_watermark = cur->offset; } } while (--cur_incomplete_it >= first_incomplete_it); return true; } /* * Recursively examine each descendant of the provided flashmap descriptor node * to ensure its position and size are known, attempt to infer them otherwise, * and validate their values once they've been populated. * This processes nodes according to the following algorithm: * - At each level of the tree, it moves laterally between siblings, keeping * a watermark of its current offset relative to the previous section, which * it uses to fill in any unknown offsets it encounters along the way. * - The first time it encounters a sibling with unknown size, it loses track * of the watermark, and is therefore unable to complete further offsets; * instead, if the watermark was known before, it marks the current node as * the first that couldn't be completed in the initial pass. * - If the current watermark is unknown (i.e. a node has been marked as the * first incomplete one) and one with a fixed offset is encountered, a * reverse lateral traversal is dispatched that uses that provided offset as * a reverse watermark to complete all unknown fields until it finishes with * the node marked as the first incomplete one: at this point, that flag is * cleared, the watermark is updated, and forward processing resumes from * where it left off. * - If the watermark is unknown (i.e. node(s) are incomplete) after traversing * all children of a particular parent node, reverse processing is employed * as described above, except that the reverse watermark is initialized to * the parent node's size instead of the (nonexistent) next node's offset. * - Once all of a node's children have been processed, the algorithm applies * itself recursively to each of the child nodes; thus, lower levels of the * tree are processed only after their containing levels are finished. * This approach can fail in two possible ways (in which case the problem is * reported to standard output and this function returns false): * - Processing reveals that some node's provided value is invalid in some way. * - Processing determines that one or more provided values require an omitted * field to take a nonsensical value. * - Processing determines that it is impossible to determine a group of * omitted values. This state is detected when a node whose offset *and* * value are omitted is encountered during forward processing and while the * current watermark is unknown: in such a case, neither can be known without * being provided with either the other or more context. * The function notably performs neither validation nor completion on the parent * node it is passed; thus, it is important to ensure that that node is valid. * (At the very least, it must have a valid size field in order for the * algorithm to work on its children.) * * @param cur_level Parent node, which must minimally already have a valid size * @return Whether completing and validating the children succeeded */ static bool validate_and_complete_info(struct flashmap_descriptor *cur_level) { assert(cur_level); assert(cur_level->size_known); // Our watermark is only known when first_incomplete_it is NULL. flashmap_descriptor_iterator_t first_incomplete_it = NULL; unsigned watermark = 0; fmd_foreach_child_iterator(cur_it, cur_level) { struct flashmap_descriptor *cur_section = *cur_it; if (first_incomplete_it) { if (cur_section->offset_known) { if (complete_missing_info_backward( first_incomplete_it, cur_it - 1, cur_section->offset)) { first_incomplete_it = NULL; watermark = cur_section->offset; } else { return false; } } // Otherwise, we can't go back until a provided offset. } else if (!cur_section->offset_known) { cur_section->offset_known = true; cur_section->offset = watermark; } assert(cur_level->size_known); struct unsigned_option max_endpoint = {true, cur_level->size}; if (cur_it != cur_level->list + cur_level->list_len - 1) { struct flashmap_descriptor *next_section = cur_it[1]; max_endpoint.val_known = next_section->offset_known; max_endpoint.val = next_section->offset; } if (!validate_descriptor_node(cur_section, (struct unsigned_option) {!first_incomplete_it, watermark}, max_endpoint)) return false; if (!cur_section->size_known) { if (!cur_section->offset_known) { ERROR("Cannot determine either offset or size of section '%s'\n", cur_section->name); return false; } else if (!first_incomplete_it) { first_incomplete_it = cur_it; } else { // We shouldn't find an unknown size within an // incomplete region because the backward // traversal at the beginning of this node's // processing should have concluded said region. assert(!first_incomplete_it); } } else if (!first_incomplete_it) { watermark = cur_section->offset + cur_section->size; } } if (first_incomplete_it && !complete_missing_info_backward(first_incomplete_it, cur_level->list + cur_level->list_len - 1, cur_level->size)) return false; fmd_foreach_child(cur_section, cur_level) { assert(cur_section->offset_known); assert(cur_section->size_known); if (!validate_and_complete_info(cur_section)) return false; } return true; } static void print_with_prefix(const struct flashmap_descriptor *tree, const char *pre) { assert(tree); assert(pre); printf("%ssection '%s' has ", pre, tree->name); if (tree->offset_known) printf("offset %uB, ", tree->offset); else fputs("unknown offset, ", stdout); if (tree->size_known) printf("size %uB, ", tree->size); else fputs("unknown size, ", stdout); printf("and %zu subsections", tree->list_len); if (tree->list_len) { puts(":"); char child_prefix[strlen(pre) + 2]; strcpy(child_prefix, pre); strcat(child_prefix, "\t"); fmd_foreach_child(each, tree) print_with_prefix(each, child_prefix); } else { puts(""); } } struct flashmap_descriptor *fmd_create(FILE *stream) { assert(stream); yyin = stream; struct flashmap_descriptor *ret = NULL; if (yyparse() == 0) ret = res; yylex_destroy(); yyin = NULL; res = NULL; if (ret) { // This hash table is used to store the declared name of each // section and ensure that each is globally unique. if (!hcreate(fmd_count_nodes(ret))) { perror("E: While initializing hashtable"); fmd_cleanup(ret); return NULL; } // Even though we haven't checked that the root node (ret) has // a size field as required by this function, the parser // warrants that it does because the grammar requires it. if (!validate_and_complete_info(ret)) { hdestroy(); fmd_cleanup(ret); return NULL; } hdestroy(); } return ret; } void fmd_cleanup(struct flashmap_descriptor *victim) { if (!victim) return; free(victim->name); for (unsigned idx = 0; idx < victim->list_len; ++idx) fmd_cleanup(victim->list[idx]); free(victim->list); free(victim); } size_t fmd_count_nodes(const struct flashmap_descriptor *tree) { assert(tree); if (!tree->list_len) return 1; unsigned count = 1; fmd_foreach_child(lower, tree) count += fmd_count_nodes(lower); return count; } const struct flashmap_descriptor *fmd_find_node( const struct flashmap_descriptor *root, const char *name) { assert(root); assert(name); if (strcmp(root->name, name) == 0) return root; fmd_foreach_child(descendant, root) { const struct flashmap_descriptor *match = fmd_find_node(descendant, name); if (match) return match; } return NULL; } unsigned fmd_calc_absolute_offset(const struct flashmap_descriptor *root, const char *name) { assert(root); assert(name); if (strcmp(root->name, name) == 0) return 0; fmd_foreach_child(descendant, root) { unsigned subtotal = fmd_calc_absolute_offset(descendant, name); if (subtotal != FMD_NOTFOUND) return descendant->offset + subtotal; } return FMD_NOTFOUND; } void fmd_print(const struct flashmap_descriptor *tree) { print_with_prefix(tree, ""); }